C++ Assert()断言机制原理以及使用方法

void assert(  
  int expression  
); 

// crt_assert.c 
// compile with: /c 
#include <stdio.h> 
#include <assert.h> 
#include <string.h> 
 
void analyze_string( char *string );  // Prototype 
 
int main( void ) 
{ 
  char test1[] = "abc", *test2 = NULL, test3[] = ""; 
 
  printf ( "Analyzing string '%s'\n", test1 ); fflush( stdout ); 
  analyze_string( test1 ); 
  printf ( "Analyzing string '%s'\n", test2 ); fflush( stdout ); 
  analyze_string( test2 ); 
  printf ( "Analyzing string '%s'\n", test3 ); fflush( stdout ); 
  analyze_string( test3 ); 
} 
 
// Tests a string to see if it is NULL,  
// empty, or longer than 0 characters. 
void analyze_string( char * string ) 
{ 
  assert( string != NULL );    // Cannot be NULL 
  assert( *string != '\0' );    // Cannot be empty 
  assert( strlen( string ) > 2 ); // Length must exceed 2 
} 

Analyzing string 'abc' 
Analyzing string '(null)' 
Assertion failed: string != NULL, file assert.cpp, line 25 
 
abnormal program termination 

int resetBufferSize(int nNewSize)
{
 //功能:改变缓冲区大小,
 //参数:nNewSize 缓冲区新长度
//返回值:缓冲区当前长度
//说明:保持原信息内容不变   nNewSize<=0表示清除缓冲区
assert(nNewSize >= 0);
assert(nNewSize <= MAX_BUFFER_SIZE);

 ...
}

Analyzing string 'abc' 
Analyzing string '(null)' 
Analyzing string '' 

void* memcpy(void *dst, const void *src, size_t count)   
{   
  //安全检查 
  assert( (dst != NULL) && (src != NULL) );   
 
  unsigned char *pdst = (unsigned char *)dst;   
  const unsigned char *psrc = (const unsigned char *)src;   
 
  //防止内存重复 
  assert(!(psrc<=pdst && pdst<psrc+count));   
  assert(!(pdst<=psrc && psrc<pdst+count));   
 
  while(count--)   
  {   
    *pdst = *psrc;   
    pdst++;   
    psrc++;   
  }   
  return dst;   
}